Enantiomer Fractions of Organic Chlorinated Pesticides in Arctic Marine Ice Fauna, Zooplankton, and Benthos

Abstract

Stereoisomers of chiral chlorinated pesticides (R-HCH (HCH ) hexachlorocyclohexane), transand cis-chlordane, MC5, o,p′-DDT) were quantified in arctic marine invertebrates (ice-associated amphipods Gammarus wilkitzkii, pelagic copepods Calanus hyperboreus, krill Thysanoessa inermis, and amphipods Themisto libellula, and benthic amphipods Paramphithoe hystrix). Enantiomer fractions (EFs) were calculated to investigate the influence of habitat, geographic area, and diet on selective bioaccumulation of the (-)or (+)-enantiomer. Depletion of the (+)-R-HCH enantionmer increased from ice fauna to zooplankton to benthos, corresponding to previous reports of EF variations with depth. Chlordanes and o,p′-DDT also showed the strongest enantioselective bioaccumulation in benthic amphipods and less so in zooplankton and ice fauna, which had closer to racemic EFs. Neither diet nor geographic area explained EF differences among samples. Nonracemic EFs in benthos may be related to stereoselective biotransformation, but is most likely reflecting vertical distribution of EFs in the water column and sediments, as demonstrated earlier for R-HCH in the Canadian and European Arctic.

Chirality as an Environmental Forensics Tool

“…Such similarity suggests that nonracemic residues of the invertebrates were due to uptake of microbially weathered a-HCH from the surroundings. Likewise, measurements of nonracemic a-HCH (EF ¼ 0.43) in Calanus near Svarbald in the European Arctic were also consistent with this hypothesis [191]. While a-HCH, cis-chlordane, MC-5, and o,p 0 -DDT EFs in the amphipod Themisto libellula were more nonracemic in benthos specimens compared to pelagic specimens (e.g.…”

“…A number of aquatic invertebrates do appear incapable of biotransforming chiral POPs. The copepod Calanus hyperboreus has almost always been observed with racemic proportions of a-HCH, cis-and trans-chlordane, heptachlor epoxide, oxychlordane, MC-5, and PCBs [189][190][191][192], consistent with this hypothesis. While a-HCH in most Northwater Polynya pelagic and benthic invertebrates, including Calanus, were nonracemic (EF range of 0.41 to 0.43), these EFs were very similar to that in Polynya waters (EF ¼ 0.45) [137].…”

“…While a-HCH, cis-chlordane, MC-5, and o,p 0 -DDT EFs in the amphipod Themisto libellula were more nonracemic in benthos specimens compared to pelagic specimens (e.g. a-HCH EFs of 0.35 versus 0.41 and o,p 0 -DDT EFs of 0.58 versus 0.51, respectively), both enantiomer and isomer compositions in this species were similar to the respective surrounding benthic or pelagic waters in all cases [191]. Thus, these observations were consistent with bioaccumulation of weathered residues as the process responsible for nonracemic EFs.…”

Polyaromatic hydrocarbons, chlorinated and brominated organic contaminants as tracers of feeding ecology in polar benthic amphipods

“…An exception to this is one P. hystrix sample that grouped with A. nugax (NBB). This sample also differed from the other P. hystrix samples in terms of enantiomeric fractions of chiral chlorinated pesticides (Borgå & Bidleman 2005), which remains unexplained.…”

Toxicities of fipronil enantiomers to the honeybee Apis mellifera L. and enantiomeric compositions of fipronil in honey plant flowers

“…Because of their different molecular configurations, enantiomers of chiral pesticides may differ in binding to structure-sensitive biological receptors or naturally occurring chiral molecules [8,9]. As a result, enantiomers can have very different toxicities [10][11][12], biological activities [13], and microbial degradation rates [14][15][16]. For example, Liu et al [12] observed drastic differences in toxicities of enantiomers of synthetic pyrethroid and organophosphate insecticides to two aquatic species, Ceriodaphnia dubia and Daphnia magna.…”